Treesearch

We tested for indirect effects of population density of large herbivores on plant species richness and diversity in a montane ecosystem, where increased net aboveground primary productivity (NAPP) in response to low levels of herbivory has been reported. We documented a positive, linear relationship between plant-species diversity and richness with NAPP. Structural equation modeling revealed significant indirect relationships between population density of herbivores, NAPP, and species diversity.We observed an indirect effect of density-dependent processes in large, herbivorous mammals and...

Western red-backed voles are endemic to western Oregon and northern California and represent a large proportion of the rodent community in mature Douglas-fir forests. Despite their dominance in these forests, little is known about their selection of home ranges. We radiotracked 23 western red-backed voles in three mature, coniferous forest stands in the southern Oregon Cascades during 1994 and 1995 and estimated home range size, movements, and habitat associations. Males had larger home ranges than females and males moved farther each evening than females. Females were most active during...

The emerging perspective of ecosystems as both non-equilibrium and dynamic fits aquatic ecosystems as well as terrestrial systems. It is increasingly recognized that watersheds historically passed through different conditions over time. Habitat conditions varied in quantity and quality, primarily as a function of the time since the last major disturbance and the legacy of that disturbance. Thus, to match the effects of historical processes, we would expect a variety of conditions to exist across the watersheds in a region at any time. Additionally, watersheds have different potentials to...

Physical inactivity, overweight, and obesity are growing national concerns owing to their associations with chronic diseases and overall well-being. Parks and recreation providers play a pivotal role in addressing these public health issues by providing the public with infrastructure that enables outdoor physical activity. Our analysis of county-level data for Oregon shows a measurable relationship between adult physical activity, overweight, obesity, and recreation supply and demand. Counties comprising more active residents are associated with healthier counties as measured by the...

A plant-bacterium association of the cardon cactus (Pachycereus pringlei) and endophytic bacteria promotes establishment of seedlings and growth on igneous rocks without soil. These bacteria weather several rock types and minerals, unbind significant amounts of useful minerals for plants from the rocks, fix in vitro N2. produce volatile and non-volatile organic acids, and reduce rock particle size to form mineral soil. This study revealed the presence of large populations of culturabIe endophytic bacteria inside the seeds extracted from wild plants, from seeds extracted from the guano of...

Knowledge of forest development is basic to understanding the ecology, dynamics, and management of forest ecosystems. We hypothesized that the age structure patterns of Douglas-fir at 205 old forest sites in western Oregon are extremely variable with long and (or) multiple establishment periods common, and that these patterns reflect variation in regional-scale climate, landscape-scale topography, and landscape-scale fire history. We used estahlishment dates for 5,892 individual Douglas-firs from these sites to test these hypotheses. We identified four groups of old forest sites with...

We examined the effect of canopy cover on adult aquatic insect emergence by collecting bi-weekly samples from twelve headwater stream reaches flowing either under a mature conifer canopy or streams flowing through ten-year-old regeneration in western Oregon from February to November 1997. Density and biomass generally followed a bimodal curve with peaks during early spring and summer. Richness was unimodally distributed across time, peaking during mid-season, when abundance began to decline. However, there was a trend showing that headwater streams flowing through young forest supported...

A plant-bacterium association between the giant cardon cactus Pachycereus pringlei and endophytic bacteria help seedlings establish and grow on barren rock, This cactus, together with other desert plants, is responsible for weathering ancient lava flows in the Baja California Peninsula of Mexico.When cardon seeds are inoculated with endophytic bacteria, the seedlings grow in pulverized rock for at least a year without fertilization and without showing distress. The bacteria-plant association released significant amounts of necessary nutrients from the substrate. When endophytic bacteria...

Seabirds maintain plasticity in their foraging behavior to cope with energy demands and foraging constraints that vary over the reproductive cycle, but behavioral studies comparing breeding and nonbreeding individuals are rare. Here we characterize how Marbled Murrelets (Brachyramphus marmoratus) adjust their foraging effort in response to changes in reproductive demands in an upwelling system in central California. We radio-marked 32 murrelets of known reproductive status (9 breeders, 12 potential breeders, and 11 nonbreeders) and estimated both foraging ranges and diving rates during the...

Over the last 20 years, changing public values and increased ecological understanding have led to a paradigm shift in forestry from timber management to sustainable ecosystem management on U.S. federal lands. Forest managers are now seeking alternative management approaches that simultaneously meet socio-cultural, ecological and economic goals. Consequently, many field experiments have become increasingly interdisciplinary and larger in scale or scope. Individually and collectively, these studies in western Washington and Oregon represent major investments by research and land management...